Known from the state of the art is an I/O apparatus, which by means of three different connection terminals can implement the following three functions: firstly, switch, respectively control, a connected, externally driven load; second, detect the presence of a passive input signal on a second connection terminal; and third, detect the presence of an active input signal on a third connection terminal. This means that, for implementing these three different functions, thus one output function and two input functions, three connection terminals are needed with a total of five connections on a circuit board. The result is a large space requirement on the circuit board, which, in turn, leads to increased costs in the construction of the I/O apparatus on a circuit board and then later causes also higher inventory costs. Therefore, it is desirable that the space required for the construction of an I/O apparatus on a circuit board be kept as small as possible.
Furthermore, I/O apparatuses are known, which at two connection terminals with three connections can detect at the first connection terminal a direct voltage signal (DC) or an alternating voltage signal (AC) as active input signal and at the second connection terminal a passive input signal. These active or passive input signals can, however, only be detected over a small voltage range, which is a disadvantage of the state of the art.